For most situations it will automatically switch between the two. If you're in a rare area (like the oil patch) where you have weak LTE but a stronger 4G signal, or need a 4G corporate private build, then I can see you needing to tell the SmartHub to force 4G over LTE.
In that case it depends on the SmartHub as to which options are available, but if you go into the admin pages for the hub, there should be a drop down toggle providing 3G/4G/LTE options for the cellular connection. Some hubs have them, some don't, or only let you check a radio button/box for LTE preferred (but unchecking that should accomplish the same thing usually).
Check if you can get the user guide for you model from the mfr, it should include the network connectivity page in the setup or troubleshooting.
